436 MODERN CLASSIFICATION OF INSECTS. 
wings being of a firmer consistence than the hind wings, and furnished 
with three strong furcate nerves; the nerves of the hind wings are 
very delicate; the abdomen is small, and terminated in the females 
by a plurivalve conical ovipositor (fig. 117. 1.), and in the males by 
several erect appendages (fig. 117. 5.). The general habit of these 
insects is very similar to that of some of the Cicadz, with which they 
also agree in their saltatorial powers and deflexed wings: hence, as 
well as from other circumstances, M. Dufour considers them inter- 
mediate between the Cicadellina and Aphides. They were named by 
Réaumur Faux Pucerons, from their relation to the Aphides ; and by 
Linneus, Chermes. Geoffroy, however, considering that the latter 
name had been improperly employed by Linnzus, gave to these in- 
sects the name of Psylla, from the Greek, in allusion to their salta- 
torial powers; whilst he employed the name of Chermes, in its more 
legitimate sense, to designate some of the Linnzan species of Coccus 
which had been employed as dyes, the names Chermes, Kermes, or 
Alkermes having been given by the Arabians and Persians to the Coccus 
llicis Zinn., or famed Tyrian dye: Geoftroy’s name has consequently 
received general adoption. 
They subsist in all their states upon plants, and have received 
specific names from the various trees and vegetables which they 
frequent. The species, however, require an attentive investigation, 
the majority being known only by their habitat, and not by any 
detailed specific description. Their larve (fig. 117. 8. larva P. 
Betule denuded) have the body very flat, the head broad, and the 
abdomen rounded behind; the tarsi are terminated by a small mem- 
branous vesicle with two ungues ; the antennz are stated by Dufour 
to consist of only one joint ; the pup (fig. 117. 9. pupa P. Betula) 
are distinguished by having four large and broad scales on the back, 
‘which are the rudimental wings. Many species in the preparatory 
stages are covered with a white cottony secretion (fig. 117. 7. larva 
P. Betule ), and their excrement forms threads or masses of a gummy 
sucreous nature. Some species also, by puncturing vegetables, in order 
to suck the sap, occasion the production of gall-like monstrosities, 
especially upon the leaves and buds. Psylla Buxi, whose history is 
traced by Réaumur (Mém. tom. iii. pl. 29. f. 1. 16.), causes the 
terminal shoots and young leaves of the box tree to assume the ap- 
pearance of buds. The same author has also represented the details 
of the history of the species which lives on the fig (tab. id. f. 17—24. 
P. Ficus Latr., LZ. Dufour, Geoffr. pl. 10. f. 2.); whilst De Geer has in 
